Conventional chain and padlock assemblies have been used in many applications for a number of years. It is usual to provide an open-linked chain and to secure this by passing the shackle of a padlock through two links of the chain. Conventional chain and padlock assemblies are frequently used in this way to secure gates or to secure equipment such as bicycles, motor vehicles or other items to a fixed object or heavy article, such as to posts or street furniture, or to anchors specifically provided for this purpose.
The conventional chain and padlock assembly has many drawbacks. For example, if the chain is of insufficient diameter or hardness, it may be cut by a suitable tool, such as a bolt cutter or hacksaw. Similarly, if the shackle on the padlock is insufficiently robust, it may be cut by a tool such as a bolt cutter. Some padlocks can be smashed or wedged open with relatively little difficulty.
It may be difficult to preserve security using a conventional chain and padlock assembly. For example, a builder may seek to protect security on a building site by surrounding the building site with a wire mesh fence and providing access only through a gate, which can be locked to the fence using a conventional chain and padlock. Apart from the weaknesses in the conventional chain and padlock assemblies referred to above, the security can be compromised if the last worker to leave the site on the day chooses to lock up the site by inserting his own padlock between the chain and the builder's padlock. This gives the worker access to the site at any time, removing control of access from the builder.
In an attempt to overcome these drawbacks, the prior art has provided lockable cables. Because these do not use open links, and because they can be provided in an armoured cable form, they can be less vulnerable to cutting or sawing than conventional open-linked chains. Further, the prior art lockable cables can be locked using an integrated keyed lock, thus eliminating the drawbacks which can be encountered with padlocks.
One such prior art locking cable is disclosed in U.S. Pat. No. 3,933,015. This discloses a flexible stranded cable on which are threaded, in a bead-like fashion, alternate ball members and socket members. As admitted in U.S. Pat. No. 3,933,015, this assembly has a weakness in that it may be possible to displace a ball member so as to expose some of the stranded cable and permit cutting of the cable with a hacksaw or other suitable tool. Once the cable is cut, all the ball members and socket members can be stripped from the cable, rendering the assembly useless as a high security device.